Meet the Happy Hormone that Helps Us Adapt to Big Changes

Perhaps there are no introductions needed, because you're probably already familiar with this happy hormone. Serotonin, the hormone that helps us regulate our moods, can also help us adapt better to changes around us.

High levels of serotonin can cause a better mood in humans, hence the nickname “happy hormone”. Studies have also found that serotonin is also able to improve our physical health. Now, a recent study, to be published on March 21st, has found that these are not serotonin's only functions.

Other earlier studies have found a connection between serotonin and the ability to adapt to changes in one's environment. A decrease in serotonin levels leads to a decrease in the ability to adapt. A team of neuroscientists at the Champalimaud Centre for the Unknown in Portugal wanted to find out how exactly this connection works.

Behavioral Flexibility

The team ran an experiment in which they reversed familiar situation some mice were in to an unfamiliar one. They trained the mice to respond in a certain way to certain rules to get a reward. The mice had to learn to associate certain odors with rewards, and other odors with the absence of rewards.

After this, the researchers inverted the rules, forcing the mice to change their learned behavior. The mice eventually learned, but for a few days, they expected to get a reward for previous odor cues. The researchers then analyzed the production of serotonin in the mouse's brain.

For the first round of tests, the researchers blocked the mice's brains from producing serotonin. They found that with impaired serotonin production, the mice were unable to adapt to the new rules of the game. In the second round of tests, however, the researchers merely monitored the production of serotonin. They found that when the mice expected a reward, their serotonin-producing neurons became more active. However, when they weren't expecting a reward, there was no change in the activity of those neurons.

An interesting and surprising thing happened when the researchers switched the rules. When this change happened, serotonin levels in the mice increased. The researchers say that this increase only happened when the mice didn't know what to expect from their situation.

Not a Happy Hormone After All

These findings raise more questions for the researchers. How does serotonin affect previously learned behavior in a situation where the behavior is not beneficial anymore? Does serotonin simply stop the behavior, or does it help anticipate erroneous behavior in an unfamiliar situation? Does serotonin perhaps have a combination of these two possible functions?

The researchers also make observations on how serotonin functions during depression. They say that depression can be the inability to adapt to difficult or even devastating situations. An increase in serotonin may help depressed people adapt to these situations and thus pull them out of depression.

Because of this, the researchers say that the nickname “happy hormone” may not be accurate after all. Perhaps, serotonin should be the “behavioral flexibility hormone” instead. Then again, a rose by any other name smells just as sweet. Be it a happy hormone or a behavioral flexibility hormone, serotonin is what drives us to adapt and thrive in the unfamiliar.